Exposure routes:

Breakdown product of chemical used in cosmetics, paint, plastic, food packaging, and other common consumer products.

Summary

Found within many consumer products, phthalates are industrial plasticizers that impart flexibility and resilience to plastic, among other uses. Mono-butyl phthalates (mBuP, including mono-n-butyl phthalate and mono-isobutyl phthalate) are metabolites, or breakdown products, of dibutyl phthalates (di-n-butyl, di-isobutyl), industrial solvents or additives used in consumer products such as nail polish, cosmetics, some printing inks, adhesives, caulks, pharmaceutical coatings, and insecticides (EWG 2003; Wolff 2007). Mono-n-butyl phthalate is also a minor metabolite of butyl benzyl phthalate (CDC 2005). Exposure to dibutyl phthalates occurs through direct use of products containing these chemicals, as well as through inhalation of air containing these chemicals (CDC 2005).

In September 2000, scientists from the Centers for Disease Control and Prevention (CDC) conducted the first accurate measurements of human phthalate exposures, and reported finding phthalates in every one of 289 people tested, at surprisingly high levels (Blount 2000). The latest exposure study from CDC indicates that mBuP is a widespread contaminant of the human body (CDC 2005). Measurements of mBuP in the urine of over 2,500 Americans indicate that women are more exposed than men, and younger children (ages 6-11) are more exposed than older children (ages 12-19) and adults (CDC 2005). In a recent study of girls age 6 to 8 spearheaded by Mount Sinai School of Medicine, these particular phthalate metabolites were found in 88 of 90 girls tested (Wolff 2007). The European Union has banned use of some phthalates in cosmetics and other consumer products, in response to concerns about exposure as well as toxicity.

Phthalates are potent toxins to the male reproductive system. High levels of mBuP are associated with reduced levels of sperm motility and concentration, and alterations in hormone levels in adult men (Duty 2003, 2004, 2005). A recent study of 134 births found marked differences in the reproductive systems of baby boys whose mothers had the highest mBuP phthalate measurements during pregnancy (Swan 2005). A second study indicates that these mothers' phthalate exposures were not extreme, but rather were typical for about one-quarter of all U.S. women (Marsee 2006). Further research documented decreased testosterone levels among baby boys exposed to mBuP in their mother's breast milk (Main 2006). High levels of mBuP are also linked to altered thyroid hormone levels in pregnant women (Huang 2007).